This application claims the benefit of the filing date of Provisional Application No. 60/013,888, filed Mar. 22, 1996. The present invention relates generally to improvements in iron smelting processes. More particularly, the invention concerns a method of reducing iron losses in an iron smelting process utilizing post-combustion steel smelting technology. The method has particular utility in smelting processes using iron ores and iron bearing oxides such as steel plant dusts and sludge, but may also be incorporated into other processes with iron bearing feedstocks.
Methods of steel production using a source of iron oxide and coal-based fuels are well known in the art. During such smelting processes, a substantial amount of dust is produced by the smelting furnace. Traditionally, the dust emitted from furnaces have been feed to sinter plants. Over the years, however, many sinter plants in the United States have been shut down for a variety of reasons. Moreover, so far as Applicants are aware, the remaining sinter plants currently in operation are limited, in most cases, to using only steel plant residuals. Steel plant dust and sludges that contain zinc are generally poor iron oxide sources for sinter plants because the zinc tends to recirculate in the furnace and form destructive accreations. In addition, steel plant residuals often contain oils (rolling mill sludge) or alkalis (blast furnace sludge) that cannot be charged to sinter plants because of environmental concerns.
Several steel plants have attempted to remedy the previously mentioned deficiencies by agglomerating steel plant residuals and recycling the same back to the blast furnace. However, this approach adversely affects the performance of the blast furnace by lowering productivity and product quality, while simultaneously increasing operating costs. Moreover, the steel plant residues often have unacceptably high levels of iron relative to zinc that prohibit recycling the sludge back to the smelter. Consequently, in most steel plants in North America, waste oxides present in plant residuals are landfilled at substantial costs to the steelmaker. However, landfilling waste oxides is not considered a long term solution for environmental reasons. Consequently, it is preferable to reduce the total volume of waste oxides that are landfilled. Accordingly, it is an object of the invention to produce an economical method of smelting that minimizes the environmental impact. To these ends, Applicants have developed a method to reduce iron loses resulting from such smelting processes.